It's no joke when a twit sends a tweet

Martin Wainwright, London

AN exasperated tweet by a British air traveller grounded by January's snow cost him £1000 ($A1650) when a court failed to see the joke in his spoof threat to ''blow an airport sky high''.

Trainee accountant Paul Chambers is the first Briton to be convicted of a criminal offence on the microblogging site Twitter.

News of his conviction on Monday at the Doncaster Magistrates Court was, appropriately, broken by disappointed and angry tweets from friends and supporters. He was told by a district judge that his message was ''of a menacing nature in the context of the times in which we live''.

Chambers, 26, tapped out on his mobile: ''Crap! Robin Hood airport is closed. You've got a week and a bit to get your shit together, otherwise I'm blowing the airport sky high!''

The tweet was sent on January 6 to his 600 followers.

The court was told that Chambers had simply suffered ''a moment of frustration'' because his plans to fly to Ireland for a blind date with one of his Twitter contacts looked ruined. He was arrested by anti-terror police at his office a week later, after a manager at the airport found the message while doing an unrelated computer search. The airport categorised the message as ''not credible'' in threat terms but was obliged to tell South Yorkshire police, who took action.

Officers later deleted the tweet and impounded his iPhone and two computers. He was fined £385 by district judge Jonathan Bennett and ordered to pay £600 costs and a £15 victims' surcharge.

Chambers lost his job as a financial supervisor at a car distribution firm in Doncaster after his arrest.